In the production of cement clinker, lime-containing raw meal is first preheated, then calcined, and finally fired to completion. Massive amounts of CO2 are released during the calcining of the limestone. A concern is therefore to reduce the CO2 emissions.
EP 2 243 754 A1 describes a method for producing a hydraulic binder which is based on a calcium silicate compound and has properties similar to those of conventional Portland cement, but where much less CO2 is released in its production. In that method, first of all, a calcium- and silicon-containing starting material is treated hydrothermally at temperatures of 120-250° C., producing a calcium silicate hydrate-containing intermediate. The intermediate is subsequently subjected to reactive milling at a temperature of 100-150° C., alone or together with another silicate-containing material, in a mill, with at least partial formation of a belite-containing binder, accompanied by reaction and dewatering, this binder being highly reactive and representing a binder comparable to Portland cement, with a low heat of reaction and a high filling strength.